1. Field of the Invention
The present invention relates to a fault detection and bandwidth monitoring means for a packet switching arrangement, such as an asynchronous time division multiplex ATDM switch between boards in a system.
2. Description of Related Art
Fault detection in a pure, asynchronous ATDM switch where replicated switch planes may not be provided or, if provided, are not synchronous with each other, will be based on error correlation techniques rather than direct plane comparison.
Traffic management in such a switch involves bandwidth monitoring to determine the actual degree of utilization of links as opposed to planned or negotiated utilization. In this context planned utilization relates to the connection set-up phase of switching where a switch path is selected according to an estimate of switch link loading based on data rates and on the statistical nature of the connections. Negotiated utilization relates to the class of service of the customer who may be charged according to quality of service criteria.
Deviations from the planned occupancy are to be expected as new connections are established during holding times of existing ones in a manner which cannot be accurately predicted. Moreover, failure conditions can cause redistribution of traffic due to re-routing around faults, including self-healing techniques.
Deviations from planned occupancy can be reduced if the switch is fully conscious of its connection types in terms of peak-to-mean bandwidth and streamed or bursty source.
Similarly deviations from negotiated occupancy can occur due to fradulent usage or to malfunction.